1. Field of the Invention
The present invention relates to a stereoscopic image display device, and more particularly to a stereoscopic image display device for seeing an image for a right eye and an image for a left eye which are displayed on a liquid crystal panel in time sharing through shutter glasses, thereby giving a solidity to the images artificially.
2. Description of the Background Art
In recent years, a stereoscopic image display device technique utilizing a binocular parallax is developed as an image display technique for artificially obtaining a solidity by a user. This is a method of seeing a display by using shutter glasses for alternately switching the image for the left eye and the image for the right eye on a time basis to display the images onto a display and closing left and right fields of view synchronously with an image switching timing, thereby separating the image for the right eye and the image for the left eye temporally and causing the user's left and right eyes to see the image for the left eye and the image for the right eye and thus giving a solidity to the images artificially.
The stereoscopic image display device has the following problem. In other words, there is an occurrence of a three-dimensional (3D) crosstalk in which an image for a left eye that is not originally incident on a right eye of an observer is incident thereon or an image for the right eye that is not originally incident on the left eye is incident thereon.
Moreover, there is a problem in that a light source to be used in a back light for emitting light at a back face of a liquid crystal panel has a luminance or a white color changed due to a variation in a temperature or aged deterioration.
As a countermeasure to be taken against these problems, there is disclosed the following technique in the liquid crystal display described in Japanese Patent Application Laid-Open No. 11-295689 (1999) (Page 3, FIG. 1). More specifically, by three types of back lights having different luminescent colors and light sensors corresponding to the luminescent colors, the luminescent colors are always caused to be equal to set values against a variation in a temperature or aged deterioration of the back lights.
In the stereoscopic image display device described in Japanese Patent Application Laid-Open No. 2010-276928 (Pages 6 to 7, FIG. 2), moreover, there is disclosed the technique for scanning a divided back light synchronously with an image to carry out lighting for a short period sequentially (back light scanning), thereby suppressing a 3D crosstalk.
Furthermore, in the image display device described in Japanese Patent Application Laid-Open No. 2011-141324 (Pages 9 to 11, FIGS. 11 and 12), the following technique is disclosed. More specifically, a 3D crosstalk is suppressed by dividing back lights to emit light for a light emission period for each of the back lights depending on a brightness of an input image signal, that is, by changing a luminance to enhance a contrast and synchronizing a light emission timing of the back light with rewrite of a liquid crystal to vary a phase, thereby emitting light sequentially for a short period.
In the case in which the back light sources having different luminescent colors are used as described in the Japanese Patent Application Laid-Open No. 11-295689 and the back light sources are divided and the light emission period of the back light is changed depending on the brightness of the input image, and the control for sequentially carrying out the scanning and the light emission is performed synchronously with the image as described in the Japanese Patent Application Laid-Open No. 2010-276928 and the Japanese Patent Application Laid-Open No. 2011-141324, there is a possibility that the light sensor might be influenced by the light quantity of the adjacent back light so that the output value of the light sensor might not constant and the luminescent color of the light source cannot be equal to the set value as a result because the back lights are divided.